1. Field of the Invention
The present invention is directed to a valve having a closure member for closing a valve orifice, particularly so as to be tight against gas, in a closed position of the closure member, wherein the closure member can be moved in a closing process by at least one actuator starting from a first position of maximum opening at least along a first partial distance with a linear movement component in direction of its closed position, and the actuator carries out a closing stroke with a linear stroke direction for a movement of the closure member with this movement component.
2. Description of Related Art
Generic valves are used, for example, in semiconductor fabrication or semiconductor machining, to carry out individual machining steps in a gastight manner in closed environments which are substantially emptied of air (i.e., vacuum environments). Often, these valves are also called vacuum valves. They are also frequently referred to as slide valves because the closure member of the valve is displaced along its path from the maximum open position to the closed position in a linear manner at least partially. As a matter of principle in such valves, care must be taken that a seal which is usually arranged at the closure member, or at the seat surface of the valve corresponding to it, is not loaded transverse to its longitudinal direction after the closure member has made contact with the sealing surface. Such shear stresses on the seals are generally acknowledged as being very detrimental to the longevity of the seal. To prevent this, various type of closure members have been developed in the prior art which are movable at least partially in a linear motion from the maximum open position to the closed position. A first group of closure members is constructed so as to be substantially wedge-shaped so that a force component presses the closure member against the seat surface perpendicular to the seat surface at the end of the closing movement of the closure member due to the wedge effect. Closure members in this type of embodiment are shown in U.S. Pat. No. 4,921,213 and U.S. Pat. No. 7,011,294. In other generic valves, the closure member is initially displaced linearly in a displacement direction by an actuator for closing the valve until the closure member is in a position in which it lies opposite to the valve orifice but so as to be raised from the valve seat. This is followed by a movement with another movement component usually oriented perpendicular to the seat surface so that the closure member is pressed against the seat surface of the valve housing. The second part of the closing movement in such slide valves is achieved in different ways. U.S. Pat. No. 6,629,682, for example, shows a generic valve in which the closure member is pressed against the seat surface of the valve housing by a tilting movement by means of another actuator. With respect to this type of valve, in which the closure member in its entirety executes an L-shaped or J-shaped movement, other variants are also known in which the closure member is pressed against the seat surface by tilting members. A design of this type is shown in DE 32 24 387.
Other variants of closure members known from the prior art are moved linearly exclusively in one direction when moving from the maximum open position into the closed position. In this case, the seat surface of the valve body is correspondingly arranged perpendicular to the movement direction of the closure member. An example is disclosed in U.S. Pat. No. 6,685,163.
It is conventional in the prior art to realize the linear movement of the closure member by means of a—usually pneumatic—piston-cylinder unit. The piston rod of this unit generally acts directly on the closure member. This has two drawbacks. First, the closing speed and opening speed that can be realized by means of these pneumatic actuators is not as high as would be desirable especially in the first movement phase. Second, the dimensions and design of these actuators must be very large in order to provide the desired closing pressures in the closed position of the closure member.
JP 6-241344 discloses a solution in which the closing stroke of the actuator, which is likewise constructed as a piston-cylinder unit, is carried out parallel to the linear closing movement of the valve body. To improve the speed and available contact pressing pressures, this reference discloses connecting the actuator to the closure member by means of gears driven by a toothed rack and arms which are eccentrically articulated at the latter. However, the construction shown in this reference is relatively complicated and requires many parts.